Probabilistic Modelling of Reliability and Maintenance of Protection Systems Incorporated into Internal Collection Grid of a Wind Farm

The capacity factor (performance) of wind farms is quite unsatisfactory and is much lower as compared to conventional power generation units. The performance refers, among others, to ‘electric and electronic components’ of wind farms, i.e. generators, transformers, cables, busbars, protection systems, power electronic units, and many more. Assuring a high availability of the components can require their high both reliability and quality of preventive and corrective maintenance strategies. Reliability and maintenance of protection systems (one or more protective relays, circuit breaker, wiring, and other components) can result in major wind farms operation upsets and substantially influence their performance. Recently, microprocessor-based electronic relays have been developed and are being applied at increasing rate. They are usually equipped with self-monitoring and checking module. Some of the protection system failures can be hidden ones, i.e. to be detected: within planned maintenance, by self-monitoring and checking module or while fault or failure of protected component occurred. Availability rate can be a main criterion of system’ reliability and maintenance. It is a probability that a system occupies up state within a long time, and can be calculate relying on semi-Markov model presented in the study. One of the application of the model can be valuable feedback and recommendations on time interval of periodic planned maintenance that maximizes the system’ availability. As an example, the optimal time interval of planned maintenance along different both failure rates and probabilities of detecting the failures, is calculated relying on the model and presented in the case study.